Many integrated circuits have multiple circuit blocks that operate at different frequencies and voltages from one another. The different frequencies and voltages allow the frequency and voltage of each circuit block to be optimized for that circuit block. Further, many integrated circuits have circuit blocks powered by dynamic voltage and frequency scaling (DVFS) in which the frequency of operation and voltage of operation of the circuit block is continuously modified to suit the current operations performed by the circuit block.
To supply the voltages to the various circuit block a separate voltage regulator module (VRM) corresponding to each circuit block is used. Due to the power dissipated, and the technology used to fabricate the VRMs, the VRMs are usually not fabricated as a circuit block on the integrated circuit that the VRMs power. The VRMs are fabricated as separate integrated circuits, and the power is delivered by an electrical wiring connection between the VRM and the integrated circuit. If the electrical wiring connection is long, ohmic resistance based voltage drops cause power losses proportional to the resistance and the square of the current. Thus, the long wiring causes the circuit block to receive a low voltage and energy is wasted in the wiring.
Furthermore, if the current supplied to the circuit block is changing with time, the inductance of the electrical wiring connection causes a significant voltage drop proportional to the rate of change of current and the inductance. As the electrical wiring connection becomes longer, both the ohmic resistance and the inductance of the electrical wiring connection become higher. Therefore, the VRM is positioned as close as possible to the circuit block of the integrated circuit driven by the VRM.
Positioning the VRM close to the integrated circuit causes noise to be induced in the integrated circuit because of the proximity of wiring that supplies the VRM with power. Therefore, as the VRM is positioned closer to the integrated circuit consideration must be given to the route that the supply wiring takes to reach the VRM.